The only online supplier that I've used so far is Scot MacDonald. His pricing on product is the best I've found, and his shipping charges are very reasonable. The only thing that could be improved on, is that his communication is sometimes great, and other times not good at all. A confirmation email when a package ships out would be a great idea, as well as prompt response to each email, even if it's just to say "Sorry, nothing yet".
Other than that, I've been completely satisfied with my transactions with him. I haven't tried Henry yet, but it sounds like I should give it a whirl.